Regression Tests

The regression test suite is located in regtest/ and uses CMake’s ctest infrastructure. Each test runs the wind_solver executable with a pre-prepared inputs.i file and terrain CSV, verifying that the solver completes without error.

Running the Tests

After building, run all regression tests from the build directory:

ctest --test-dir build -L regtest --output-on-failure

Or use the custom CMake target:

cmake --build build --target regtest

To run a single named test:

ctest --test-dir build -R flat_terrain --output-on-failure

Test Descriptions

flat_terrain

Location: regtest/flat_terrain/

Purpose: Verifies that the MLMG Poisson solver converges on the simplest possible geometry — a flat domain with all terrain elevations set to z = 0.

Terrain: A 3 × 3 grid of points spanning 0–100 m in x and y, all at z = 0 m.

Grid: 2 × 2 × 2 cells (dx = dy = dz = 50 m, domain_height = 100 m).

Wind: U_ref = 5 m/s (westerly), z_ref = 10 m, z₀ = 0.1 m.

Expected behaviour: On a flat domain the initial log-law field is horizontally uniform, so ∇·**u**₀ ≈ 0 everywhere. The MLMG solve converges immediately and the post-correction divergence should be negligible.

Key input parameters:

terrain_file  = terrain.csv
U_ref         = 5.0
V_ref         = 0.0
z_ref         = 10.0
z0            = 0.1
dx            = 50.0
dy            = 50.0
dz            = 50.0
domain_height = 100.0
mlmg_verbose  = 0
plot_file     = plt_flat_terrain

gaussian_hill

Location: regtest/gaussian_hill/

Purpose: Verifies terrain-following wind initialisation and mass-consistent correction on a realistic hill geometry.

Terrain: An 11 × 11 point cloud over a 300 × 300 m domain with a Gaussian hill of peak elevation 50 m at the domain centre (σ = 60 m).

Grid: 10 × 10 × 6 cells (dx = dy = 30 m, dz = 25 m, domain_height = 100 m).

Wind: U_ref = 10 m/s (westerly), z_ref = 10 m, z₀ = 0.03 m (short grass).

Expected behaviour: The log-law profile accelerates over the hill crest and decelerates in the lee. The mass-consistent correction adjusts the vertical velocity to enforce ∇·u = 0, producing a physically consistent flow. The test also writes a terrain-aligned CSV extract at 15 m AGL.

Key input parameters:

terrain_file  = terrain.csv
U_ref         = 10.0
V_ref         = 0.0
z_ref         = 10.0
z0            = 0.03
dx            = 30.0
dy            = 30.0
dz            = 25.0
domain_height = 100.0
alpha_h       = 1.0
alpha_v       = 1.0
mlmg_verbose  = 0
extract_agl   = 15.0
extract_file  = wind_extract.csv
plot_file     = plt_gaussian_hill

Adding New Tests

Create a new sub-directory under regtest/, e.g. regtest/my_test/.
Add a terrain file terrain.csv (X Y Z columns).
Write an inputs.i with the desired solver parameters.
Register the test in regtest/CMakeLists.txt:
```
add_regression_test(my_test my_test)
```

Re-run CMake to pick up the new test:

cmake -S . -B build
ctest --test-dir build -R my_test --output-on-failure

CI Integration

The Linux and macOS builds in .github/workflows/cmake_build.yml run the full regression suite automatically after each successful build:

ctest --test-dir build -L regtest --output-on-failure

This ensures that every push and pull request verifies both compilation and solver correctness on multiple operating systems.